There are two types of reinforcement:
1) Unconditioned reinforcement
2) Conditioned reinforcement
An unconditioned reinforcer, or primary reinforcer, is something that is necessary for the dog’s survival, or something the dog very much likes, and therefore, the dog does not need to learn that this thing is rewarding. Not each unconditioned reinforcer will have the same value for each dog. Some examples of unconditioned reinforcement include: food, air, water, shelter, toys, praise, and petting. The dog (NOT the owner or trainer) determines what their unconditioned reinforcers are.
A conditioned reinforcer, or secondary reinforcer, is something that does not inherently mean anything to the dog. The dog learns to associate the conditioned reinforcer as a good thing. Some examples of conditioned reinforcers include: walks, food bag noise, toys, “good” or “yes,” the sound of a clicker, and the doorbell. The best example of teaching a dog a conditioned reinforcer is using the “good” or “yes” cue to mark behavior. Using this cue at the instant your dog performs a desired behavior increases the communication between human and dog. The dog learns to make a positive association between your marker word (good or yes) and a food reward.